| Acronym | Definition |
|---|
| S&I | Strategy and Innovation (various companies) |
| S&I | Science & Industry (gaming, Half-Life mod) |
| S&I | Security and Intelligence (various organizations) |
| S&I | Savings and Investment |
| S&I | Systems and Information |
| S&I | Supply and Installation |
| S&I | Supervision and Inspection (USACE) |
| S&I | Salt and Ice |
| S&I | Supervision and Interpretation (medical) |
| S&I | Survey & Investigation |
| S&I | Sensing and Imaging (terahertz science) |
| S&I | Science and Innovation Network (British Foreign and Commonwealth Office; UK) |
| S&I | Suction and Irrigation (surgery) |
| S&I | Standardization & Interoperability |
| S&I | Seminaries and Institutes of Religion |
| S&I | Switchgear and Instrumentation Limited (electrical control) |